Objects have been photographed and digitized for analysis by computers. The image captured by a camera may be comprised of hundreds of thousands of pixel elements which are electronically captured by a computer and stored as a series of numbers in the computer's memory. Individual pixels having different intensities or colors may be selected to define a test set which is approximated by a box in color space. This box is then used to discriminate among the pixels comprising all or a portion of the image. For example, the intensities or colors used in the test set may be approximated by either a two-dimensional square or a three-dimensional cube. However, approximating the variation of colors in the test set by a box, ingnores the covariance between the colors of this test set. The adversely affects the resolution of the discrimination. If there is considerable covariance in the test set of colors, then to include all the colors of the test set may require a box so big that it also includes a multitude of undesirable points. Alternatively, to exclude the undesirable points may require a box so small that it does not include desired points of the test set of colors. The method of the present invention circumbents this problem by implicitly including the covariance of the colors in its analysis. Thus when conducting a detailed examination of certain characteristics of an object, points may be defined on the object which are either extraneous or excluded from the test set. This problem particularly arises in enhancing certain photographic images based upon some characteristic, regardless of the frequency of interest, e.g. frequency spectrum. U.S. Pat. Nos. 4,876,457 and 4,742,233, both assigned to AT&T, and U.S. Pat. No. 4,791,589 assigned to Tektronix, Inc. describe methods and apparatus for digitally photographing objects and discriminating features of the objects using brightness or similar characteristic.
It is well known that hydrocarbons fluoresce under ultraviolet light. Ultraviolet light has been used since the 1940's to determine whether a substrate contains hydrocarbons. For example, the geologist at the well site may determine if hydrocarbons are present in the formation by examining well cuttings under ultraviolet light. Similarly, core samples taken from the bore hole may also be examined under ultraviolet light to show the presence of hydrocarbons. Such a service is offered by Core Laboratories, a division of Western Atlas International, Inc. To document the findings of a laboratory examination, photographs were taken of cross-sections of cores taken under both natural and ultraviolet light. The service provided visual documentation of the rock type, and a visual representation of the extent of hydrocarbons present in the core. This provided the geologist a tool to better evaluate the reservoir.
Estimation of the amount and type of hydrocarbons using fluorescence initially was a subjective analysis. The fluorescence of a sample will vary according to the reservoir rock type and the API gravity of the hydrocarbon. A geologist's estimation will naturally vary between samples of the same rock type because the eye cannot distinguish subtle difference between brightness and/or colors of the fluorescence. The instant invention will greatly improve this technique and will perform the function consistently for every sample.
There has been a long felt yet unsolved need to provide an improved method for conducting digital photography of objects. Similarly, a long felt yet unsolved need existed for a method of consistently discriminating certain feature of objects. Such a need exists in the field of core analysis.